This invention relates to implantable cardiac stimulators and more particularly to a system for discriminating among cardiac depolarization waveform types, for use in cardiac pacers and anti-tachycardia devices.
In the context of a cardiac stimulator, it is often desirable to be able to distinguish between different types of depolarization waveforms. For example, it is desirable to know whether a ventricular depolarization represents a normally conducted depolarization or an ectopic depolarization (PVC or ventricular tachycardia depolarization). In the context of cardiac pacemakers, the time order of atrial and ventricular depolarizations has typically been employed to distinguish between normally conducted depolarizations and PVCs. For example, see U.S. Pat. No. 4,407,287, issued to Herpers et al. In the context of implantable cardioverters and defibrillators, waveform analysis of detected depolarizations has often been suggested for use in distinguishing among various types of depolarizations. For example, measurement of R-wave width is disclosed as early U.S. Pat. No. 3,857,398, issued to Rubin et al., in the context of an implantable defibrillator, with more sophisticated waveform analysis circuitry to distinguish normally conducted from ectopic beats disclosed in U.S. Pat. No. 4,552,154, issued to Hartlaub et al, both of which are incorporated herein by reference in their entireties.